1. Field of the Invention
This invention relates to a new and improved method and apparatus for operating and regenerating ion exchangers.
More particularly, the invention provides a new process for operating and regenerating fixed bed ion exchangers on a continuous basis without the need for moving the bed or closing down operations during the regeneration step.
2. Prior Art
There is a need in industry, and particularly the metallurgy and water purification industry, for an efficient process for removing ions from solution. The need is particularly important in the extraction of low concentrations of rare metals from leach solutions in major industrial extraction processes. Such procedures would include the removal of copper, uranium, gold, silver, etc. from the streams containing such components such as may be found in the extractive metallurgy industry.
It has been found that certain inorganic materials, such as zeolites, and synthetic organic resins, such as styrene copolymers, having axionic or cationic functional groups, such as sulfonic acid groups, readily extract metallic ions and can be used successfully to remove low concentrations of ions from feed solutions. The synthetic resins of this type have been found to be particularly useful for this purpose and have found wide use in the hydrometallurgy industry, etc. Such resins, for example, are able to concentrate metals from leaching concentrations of 6 ppm up to a concentration of about 1200 ppm.
After a period of use, however, the ion exchange resins decrease in activity due to saturation of the resins with the ions removed and the bed is said to become exhausted. Before the beds can be used again they must undergo regeneration. This is generally accomplished by stopping the process, removing the resin bed to a second chamber where it may be scrubbed to remove the impurities and is treated with a stripping solution, such as nitric acid, to remove the ions attached to the synthetic resin.
Methods used in the past for the regeneration of ion exchangers are disclosed in U.S. Pat. Nos. 2,572,848, 3,193,198, 3,240,699 and 3,394,079. These procedures are limited, however, in that they either involve stopping the reaction for removal of the resin to a second location or circulating the resin which effects destruction of the resin during movement. Furthermore, there has been hydraulic destruction of the resin at the inlet port and/or outlet port of the ion exchange vessel when the fluid flow has not been restricted. Others use a countercurrent flow where the regenerating fluid flows countercurrent to the direction of flow of the feed.